Regio‐ and Stereoselective Lipase‐Catalysed Acylation of Methyl α‐ D ‐Glycopyranosides with Fluorinated β‐Lactams

Burkholderia cepacia lipase (lipase PS‐D) catalysed acylation with 3,3‐difluoro‐4‐phenyl‐, ‐thiophen‐3‐yl‐ and ‐4‐pyridylazetidin‐2‐ones was examined for the formation of N‐Boc‐protected 6‐O‐acylated sugar–β‐amino acid conjugates from methyl α‐D‐galacto‐, ‐gluco‐ and mannopyranosides and Boc2O. The 6‐O‐acylated glycopyranoside–β‐amino acid conjugates were isolated and characterized. The low solubility of the gluco‐ and mannopyranosides and the high reactivity of the pyridylazetidinone restricted product formation. Activation of the β‐lactam ring by the presence of fluorine substituents was shown to be necessary for the enzymatic acylation reaction. The (S)‐enantiomers of the racemic β‐lactam substrates reacted with the sugars.